Films coated with paint

ABSTRACT

The present invention relates to films which are coated with at least two paint coats ( 2 ) ( 3 ), whereby the backing film ( 1 ) is coated with at least one radiation-hardenable paint coat ( 2 ) and at least one second paint coat ( 3 ), which can harden at least partially without radiation. The invention also relates to a method for producing said films and to their use for coating steel, aluminium and plastic substrates.

The present invention relates to films coated with at least two paintlayers, to a process for producing the films, and to their use.

With the nowadays customary wet-chemical finishing by way of sprayingtechniques it is extremely difficult to produce matching-color coatingson different substrates such as steel, aluminum, and plastic. The motorvehicle industry in particular is therefore interested in developing newfinishing technologies for this area.

Films are being discussed as a long-term alternative to the conventionalwet finishing. Coating with films can both economically andenvironmentally be an interesting future technology as an alternative towet finishing. Paint from the roll, guaranteeing consistent colorquality, enables a modular, site-independent production regime to beimplemented, with corresponding cost savings in manufacture. With thefilm coating of rail vehicles as well there are savings: for example,the application of multicolor contrast stripes requires for each colorthe operations of masking, spraying, and drying for 1 to 2 days. Thisentails expensive factory standing times. Through the direct laminationof colored paint film stripes it is possible to reduce significantly thestanding times and the labor involved. As well as economic aspects thereare environmental incentives as well: no emission problems with solventin the painting plant, and eco-friendly coating through solventrecycling in the coating operation.

In the prior art a variety of possible solutions have already beendiscussed. For instance, EP-A-374551 discloses coated substratessuitable for producing body-mounted components for automobile bodies.The coated substrates described in EP-A-374551 consist of metal sheetsfinished with at least one paint layer or of composites whose surfacelayer is composed of the painted metal sheets. DE-4424290.9-A1discloses, further, substrates coated with two or more layers. Thesesubstrates are deformed and processed further with the aid, whereappropriate, of additional materials. In this way it is possible toproduce body-mounted components for vehicle bodies.

Films coated with coating materials are also described in EP 0395226, EP0361823, U.S. Pat. No. 5,268,215, U.S. Pat. No. 6,063,230, DE 19526478A1, and DE 3042156 A1.

A very wide variety of materials have been conceived as carrier films.From DE-4319519 A1, U.S. Pat. No. 4,933,237, and EP 0285071, forexample, the use of polyester films is known.

Thermal coating materials are extensively used for the coating of thecarrier films. However, coating materials curable with UV radiation havealso been trialed. Such materials are described in, for example, DE19535935 A1 and DE 4439350 A1.

Different adhesion promoters have been described for the application ofthe carrier films: reference may be made in this context, for example,to DE 4319519 A1 and U.S. Pat. No. 4,933,237.

The coated films known to date have a variety of drawbacks. Theseconcern in particular the thermoformability and the consistency ofshade. Problems are also presented by the joining of the individualpaint layers and the adhesion to the substrate. Finally, in terms ofmechanical stability, the film paints have not to date been able tomatch conventional spray paints.

That is, the requirements in terms of fracture resistance, scratchresistance, chemical resistance, and weathering stability have not todate been met by the coated films. It has likewise not been possible sofar to produce metallic effects in spray paint quality.

It is an object of the present invention, accordingly, to provide filmscoated with at least two paint layers, constituting a useful alternativeto the hitherto customary liquid paints. The cold formability andthermoformability of the films and the consistency of shade, inparticular, ought to be ensured. Additionally, improved adhesion of theindividual paint layers ought to be achieved. Finally, in terms of themechanical strength, and in particular with regard to the fractureresistance, an improvement ought to be obtained over the prior art. Atthe same time the paint layers ought to exhibit scratch resistance,chemical resistance, and weathering stability comparable with those ofthe existing liquid paints. An objective of the invention, moreover, isto produce metallic effects in a quality which matches that of theexisting spray paint. Finally, it is an object of the invention toproduce films which can be removed again without residues.

The inventive solution are films coated with at least two paint layers,wherein a carrier film bears at least one first paint layer, which isradiation-curable, and at least one second paint layer, which is curableat least partly without radiation exposure. The second paint layer istherefore preferably at least partly thermally curable.

The radiation-curable paints are used particularly for the first paintlayer. Preference is given to using radiation-curable clearcoat paints.It is also possible, however, to color and/or to pigment the clearcoatpaints.

Clearcoat paints used are compositions curable with high-energyradiation, such as UV radiation or electron beams, especially UVradiation. A key constituent of such clearcoat paints is at least oneradiation-curable oligomeric or polymeric binder.

The oligomers or polymers used as binders usually have a number-averagemolecular weight of from 500 to 50 000, preferably from 1 000 to 5 000.They preferably have a double bond equivalent weight of from 300 to 2000, more preferably from 400 to 900. Furthermore, the fully formulatedbinders have a viscosity at 23° C. of preferably from 250 to 11 000mPas. They are preferably employed in an amount of from 5 to 50% byweight, more preferably from 6 to 45% by weight, more preferably stillfrom 7 to 40% by weight, very preferably from 8 to 35% by weight, and inparticular from 9 to 30% by weight, based in each case on the solids ofthe clearcoat paint.

Examples of suitable binders come from the oligomer and/or polymerclasses of (meth)acryloyl-functional (meth)acrylic copolymers, polyetheracrylates, polyester acrylates, polyesters, epoxy acrylates, urethaneacrylates, amino acrylates, melamine acrylates, silicone acrylates, andphosphazene acrylates, and the corresponding methacrylates, as describedin, for example, German patent DE 197 09 467 C1, page 4 line 36 to page5 line 61. It is preferred to use binders free from aromatic structuralunits. Preference is therefore given to using urethane (meth)acrylates,phosphazene (meth)acrylates and/or polyester (meth)acrylates, morepreferably urethane (meth)acrylates, especially aliphatic urethane(meth)acrylates.

The urethane (meth)acrylates are obtained by reacting a diisocyanate orpolyisocyanate with a chain extender from the group consisting ofdiols/polyols and/or diamines/polyamines and/or dithiols/polythiolsand/or alkanolamines and subsequently reacting the remaining freeisocyanate groups with at least one hydroxyalkyl (meth)acrylate orhydroxyalkyl ester of other ethylenically unsaturated carboxylic acids.

The amounts of chain extenders, di- and/or polyisocyanates, andhydroxyalkyl esters are preferably chosen such that

-   1.) the equivalent ratio of the NCO groups to the reactive groups of    the chain extender (hydroxyl, amino and/or mercaptyl groups) is    between 4:1 and 1:2, preferably between 3:1 and 3:2, and-   2.) the OH groups of the hydroxyalkyl esters of the ethylenically    unsaturated carboxylic acids are present in a stoichiometric amount    with respect to the remaining free isocyanate groups of the    prepolymer formed from isocyanate and chain extender.

A further option is to prepare the urethane (meth)acrylates by firstreacting some of the isocyanate groups of the diisocyanate orpolyisocyanate with at least one hydroxyalkyl ester and subsequentlyreacting the remaining isocyanate groups with a chain extender. In thiscase too the amounts of chain extender, isocyanate, and hydroxyalkylester are chosen such that the equivalent ratio of the NCO groups to thereactive groups of the chain extender is between 4:1 and 1:2, preferablybetween 3:1 and 3:2, and the equivalent ratio of the remaining NCOgroups to the OH groups of the hydroxyalkyl ester is 1:1. It will beappreciated that any forms intermediate between these two methods arealso possible. For example, some of the isocyanate groups of adiisocyanate can first be reacted with a diol, then a further fractionof the isocyanate groups can be reacted with the hydroxyalkyl ester,after which the remaining isocyanate groups can be reacted with adiamine.

Flexibilization of the urethane (meth)acrylates is possible, forexample, by reacting corresponding isocyanate-functional prepolymers oroligomers with relatively long-chain aliphatic diols and/or diamines,especially aliphatic diols and/or diamines having at least 6 carbonatoms. This flexibilization reaction can be conducted before or afterthe addition reaction of acrylic and/or methacrylic acid with theoligomers and/or prepolymers.

As examples of suitable urethane (meth)acrylates mention may be made,among others, of the following, commercially available, polyfunctionalaliphatic urethane acrylates:

-   -   Crodamer® UVU 300 from Croda Resins Ltd., Kent, United Kingdom;    -   Genomer® 4302, 4235, 4297 or 4316 from Rahn Chemie, Switzerland;    -   Ebecryl® 284, 294, IRR 351, 5129 or 1290 from UCB, Drogenbos,        Belgium;    -   Roskydal® LS 2989 or LS 2545 or V94-504 from Bayer AG, Germany;    -   Viaktin® VTE 6160 from Vianova, Austria; or    -   Laromer® 8861 from BASF AG and experimental modifications        thereof.

The systems listed here are liquid as 100% formulations. The converse ofthis is the urethane acrylate system we use with preference which issolid in the 100% state, advantageous for storage and transport.Castable solutions are produced on site from the solid resin. Solventssuitable for this purpose include THF, acetone, MEK, and MIBK.

Hydroxyl-containing urethane (meth)acrylates are known from, forexample, patent U.S. Pat. No. 4,634,602 A or U.S. Pat. No. 4,424,252 A.

One example of a suitable polyphosphazene (meth)acrylate is thephosphazene dimethacrylate from Idemitsu, Japan.

In addition, the clearcoat paints can comprise the additives,photoinitiators, and reactive diluents described in German patent DE 19709 467 C1, page 5 line 62 to page 6 line 30, including additives such aslight stabilizers, slip additives, polymerization inhibitors, flattingagents, defoamers, leveling agents, and film-forming auxiliaries.

In order to prevent the formation of bubbles due to excessively rapidsolvent release during the drying operation it is possible withpreference to add high boilers to the clearcoat paint. Their fractioncan amount to from 5% to 60%, preferably from 10% to 30%. High boilerswhich can be used include dioxane, toluene, and ethyl acetate; butylacetate is employed with preference.

The layer thickness of the clearcoat paints is from 1 μm to 400 am,preferable 5 μm to 100 μm, more preferably 15 μm to 60 μm. In principlethe choice of layer thickness depends on the stretching of the film. Theminimum layer thicknesses stated refer to the end product, i.e., agenerally stretched film.

The paints which can be cured at least partly without radiationpreferably comprise the color layers, which at the same time form thetopcoat layer. Here it is also possible to employ the automotiverefinish paints known from the prior art, on the basis of their goodphysical drying properties and ready availability.

Suitable refinish paints are one-component or multicomponent systems.Two-component systems comprise, as is known, at least one compound, inparticular a binder, having isocyanate-reactive functional groups, suchas thiol, hydroxyl, and primary and secondary amino groups, especiallyhydroxyl groups, and at least one polyisocyanate.

Examples of suitable binders are random, alternating and/or block,linear and/or branched and/or comb addition (co)polymers ofethylenically unsaturated monomers, or polyaddition resins and/orpoly-condensation resins. For further details of these terms refer toRömpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart,N.Y., 1998, page 457, “polyaddition” and “polyaddition resins(polyadducts)”, and also pages 463 and 464, “polycondensates”,“polycondensation”, and “polycondensation resins”, and also pages 73 and74, “binders”.

Examples of suitable addition (co)polymers are (meth)acrylate(co)polymers or partially hydrolyzed polyvinyl esters, especially(meth)acrylate copolymers.

Examples of suitable polyaddition resins and/or polycondensation resinsare polyesters, alkyds, polyurethanes, polylactones, polycarbonates,polyethers, epoxy resin-amine adducts, polyureas, polyamides,polyimides, polyester-polyurethanes, polyether-polyurethanes orpolyester-polyether-polyurethanes, especially polyester-polyurethanes.

Of these binders, the (meth)acrylate (co)polymers have particularadvantages and are therefore used with particular preference.

Preparation processes for (meth)acrylate copolymers are described inEuropean patent application EP 0 767 185 A1, German patent DE 22 14 650B1 or DE 27 49 576 B1, and American patents U.S. Pat. No. 4,091,048 A1,U.S. Pat. No. 3,781,379 A1, U.S. Pat. No. 5,480,493 A1, U.S. Pat. No.5,475,073 A1 or U.S. Pat. No. 5,534,598 A1 or in the standard workHouben-Weyl, Methoden der organischen Chemie, 4th edition, volume 14/1,pages 24 to 255, 1961. Suitable reactors for the copolymerizationinclude the conventional stirred tanks, stirred tank cascades, tubereactors, loop reactors or Taylor reactors, as described in, forexample, the patents and patent applications DE 1 071 241 B1, EP 0 498583 A1 or DE 198 28 742 A1 or in the article by K. Kataoka in ChemicalEngineering Science, volume 50, issue 9, 1995, pages 1409 to 1416.

The fraction of binders in the refinish paints may vary widely and isguided by the requirements of the case in hand. They are preferablyemployed in an amount of from 5 to 90% by weight, more preferably from 6to 80% by weight, more preferably still from 7 to 70% by weight, verypreferably from 8 to 60% by weight, and in particular from 9 to 50% byweight, based in each case on the solids of the refinish paint.

The polyisocyanates may have aliphatic, cycloaliphatic or aromaticparent structures. It is also possible, however, for at least two ofthese structures to be present in one polyisocyanate. For example, apolyisocyanate is considered aliphatic if its isocyanate groups aredirectly connected exclusively to aliphatic groups. Where the isocyanategroups are directly connected both to aliphatic and to cycloaliphaticgroups, the polyisocyanate in question is an aliphatic-cycloaliphaticpolyisocyanate.

Preference is given to using aliphatic, aliphatic-cycloaliphatic,cycloaliphatic, and aromatic polyisocyanates.

The aromatic polyisocyanates are preferably used when a certainyellowing tendency can be tolerated in the films of the invention. Wherethe absence of yellowing is very critical, on the other hand, it ispreferred to use aliphatic, cycloaliphatic, andaliphatic-cyclo-aliphatic polyisocyanates.

Examples of suitable polyisocyanates are isocyanato-containingpolyurethane prepolymers, which can be prepared by reacting polyols withan excess of aliphatic, aliphatic-cycloaliphatic, cycloaliphatic, andaromatic diisocyanates and are preferably of low viscosity.

Examples of suitable aromatic diisocyanates include tolylidene 2,4- or2,6-diisocyanate, phenylene 1,2-, 1,3- or 1,4-diisocyanate, naphthylene1,2-, 1,3- or 1,4-diisocyanate or di(4-isocyanatophen-1-yl)methane or-propane.

Examples of suitable aliphatic, cycloaliphatic, andaliphatic-cycloaliphatic diisocyanates are isophorone diisocyanate(i.e., 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane),5-isocyanato-1-(2-iso-cyanatoeth-1-yl)-1,3,3-trimethylcyclohexane,5-iso-cyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclo-hexane,5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane,1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane,1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane,1-isocyanato-2-(4-isocyanatobut-1-yl)-cyclohexane,1,2-diisocyanatocyclobutane, 1,3-diisocyanatocyclobutane,1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane,1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane,1,4-diisocyanatocyclohexane, dicyclohexylmethane 2,4′-diisocyanate,tri-methylene diisocyanate, tetramethylene diisocyanate, pentamethylenediisocyanate, hexamethylene diioscyanate (HDI), ethylethylenediisocyanate, trimethylhexane diisocyanate, heptamethylene diisocyanate,methylpentane diisocyanate (MPDI), nonane triisocyanate (NTI) ordiisocyanates derived from dimer fatty acids, as sold under thecommercial designation DDI 1410 by Henkel and described in patents WO97/49745 and WO 97/49747, especially2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentylcyclohexane, or 1,2-, 1,4-or 1,3-bis(isocyanatomethyl)cyclohexane, 1,2-, 1,4- or1,3-bis(2-isocyanatoeth-1-yl)cyclohexane,1,3-bis(3-iso-cyanatoprop-1-yl)cyclohexane, 1,2-, 1,4- or1,3-bis(4-isocyanatobut-1-yl)cyclohexane or liquidbis(4-iso-cyanatocyclohexyl)methane with a trans/trans content of up to30% by weight, preferably 25% by weight, and in particular 20% byweight, as described by patent applications DE 44 14 032 A1, GB 1220717A1, DE 16 18 795 A1 or DE 17 93 785 A1, preferably isophoronediisocyanate,5-isocyanato-1-(2-isocyanato-eth-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane,1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane,1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane,1-isocyanato-2-(4-isocyanatobut-1-yl)cyclohexane or HDI, especially HDI.

It is also possible to use polyisocyanates (B) containing isocyanurate,biuret, allophanate, imino-oxadiazinedione, urethane, urea, carbodiimideand/or uretdione groups, prepared in conventional manner from theabove-described diisocyanates. Examples of suitable preparationprocesses and polyisocyanates are known from, for example, patents CA1,163,591 A, U.S. Pat. No. 4,419,513, U.S. Pat. No. 4,454,317 A, EP 0646 608 A, U.S. Pat. No. 4,801,675 A, EP 0 183 976 A1, DE 40 15 155 A1,EP 0 303 150 A1, EP 0 496 208 A1, EP 0 524 500 A1, EP 0 566 037 A1, U.S.Pat. No. 5,258,482 A1, U.S. Pat. No. 5,290,902 A1, EP 0 649 806 A1, DE42 29 183 A1 or EP 0 531 820 A1 or are described in German patentapplication DE 100 05 228.2, unpublished at the priority date of thepresent specification.

Further suitable polyisocyanates include the adducts, described inGerman patent application DE 196 09 617 A1, of polyisocyanates withoxazolidines, dioxolanes, and dioxanes containing isocyanate-reactivefunctional groups, which still contain free isocyanate groups or areused in combination with other polyisocyanates.

The amount of polyisocyanates in the coating materials may vary verywidely and is guided by the requirements of the case in hand, inparticular by the amount of isocyanato-reactive groups in theconstituents. The amount is preferably from 5 to 50% by weight, morepreferably 6 to 45% by weight, more preferably still from 7 to 40% byweight, very preferably from 8 to 35% by weight, and in particular from9 to 30% by weight, based in each case on the solids of the coatingmaterial of the invention.

The refinish paints further comprise constituents which render themradiation-curable.

Examples of suitable radiation-curable constituents are theabove-described radiation-curable binders as used in the clearcoatpaints. The radiation-curable binders may additionally contain theisocyanate-reactive functional groups described above.

Further examples of suitable radiation-curable constituents areisocyanato acrylates, which contain free isocyanate groups and groupscontaining double bonds.

Highly suitable double bonds are present in, for example,(meth)acrylate, ethacrylate, crotonate, cinnamate, vinyl ether, vinylester, ethenylarylene, dicyclopentadienyl, norbornenyl, isoprenyl,isopropenyl, allyl or butenyl groups; ethenylarylene ether,dicyclopentadienyl ether, norbornenyl ether, isoprenyl ether,isopropenyl ether, allyl ether or butenyl ether groups; orethenylarylene ester, dicyclopentadienyl ester, norbornenyl ester,isoprenyl ester, isopropenyl ester, allyl ester or butenyl ester groups.Of these, (meth)acrylate groups, especially acrylate groups, are ofparticular advantage and are therefore used with very particularpreference.

The isocyanato acrylates can be prepared by reacting the above-describedpolyisocyanates with compounds which have an isocyanate-reactivefunctional group and at least one group containing double bonds.Examples of suitable compounds of this kind are 2-hydroxyethyl acrylate,2- and 3-hydroxypropyl acrylate, 2-, 3-, and 4-hydroxybutyl acrylate,reaction products thereof with epsilon-caprolactone, or allyl alcohol.For further details refer to European patent application EP 0 928 800A1.

The refinish paints may further comprise at least one of the additivesdescribed in German patent application DE 199 20 799, page 7 line 6 topage 8 line 37.

Leveling agents are preferably added to the automotive refinish paintsand to the clearcoat paints in order to achieve effectiveclearcoat/colorcoat wetting.

Examples of suitable leveling agents are described in Römpp LexikonLacke und Druckfarben, Georg Thieme Verlag, Stuttgart, N.Y., 1998,“leveling agents (assistants)”, page 602, or in Johan Bieleman,“Lackadditive” [Additives for coatings], Wiley-VCH, Weinheim, N.Y.,1998, “6.1.2 commercial leveling additives” pages 177 to 181.Flurosurfactants are used with preference. Fluorosurfactants arecommercial products and are sold, for example, by 3M under the brandname Fluorad® FC-171, -129, -170C, -430 or -431.

The pigmented paints which can be used with preference in accordancewith the invention include those curable thermally and by means ofradiation (dual cure systems, as they are known). In this case, first,an application of the liquid paints is made. At this stage they have alow viscosity. Thermal curing here produces an elastomeric coating whichby subsequent crosslinking and radiation exposure can be crosslinkedfurther.

In this way, for example, from the above-described isocyanate acrylatesand the hydroxyl-containing binders it is possible first to produce apolyurethane network which is subsequently crosslinked, by exposure toradiation, to form polyurethane-polyacrylate.

The layer thicknesses after the stretching of the topcoat paints used inaccordance with the invention are from 10 μm to 60 μm, preferably from15 μm to 40 μm. As with the layer thickness of the clearcoat paints, thetopcoat layer thickness depends on the chosen stretching.

For the radiation curing of the clearcoat layer and of the pigmentedlayer preferential consideration is given to electron beams and UVradiation. Curing with UV radiation is preferred according to theinvention.

Where the dual cure systems are employed a particular advantage is thecombination of the properties of a conventional 2-component system witha UV-crosslinking system. The elastomeric characteristics at roomtemperature achieve very good formability, while after radiationexposure effective crosslinking at the join with the clearcoat paint isobtained. Moreover, in the inventive combination of radiation-curablelayer and at least partly radiation-curable layer, the layers describedexhibit particular adhesion to one another, especially if thelast-mentioned layer is a dual cure system. Nor is this adhesion lostunder thermal or mechanical influences.

In the development of the subject matter of the invention the locatingof suitable carrier films presented problems. Surprisingly it was foundthat especially good results are achieved with unoriented polypropylenefilms. These films are readily coatable on coating machines and, afterthe paint system has cured, can be detached from the carrier film. Theformability is excellent. In accordance with the invention it has nowsurprisingly been found that, preferably at a carrier film thickness of75 μm or less, both effective formability and adequate thermal stabilityare achieved. The invention accordingly uses carrier films which arepreferably <100 μm, having more preferably a thickness >40 μm.Thicknesses of 50 μm to 70 μm are particularly preferred. Veryparticular preference attaches to 50 μm to 60 μm.

Problems with the thermal stability of the film to be coated can bereduced by using slip films. It is preferred here to use polyester filmsin a thickness of from 10 μm to 100 μm. From 18 μm to 75 μm areparticularly preferred.

The carrier film coated with the paints can be used for coating a verywide variety of substrates. In accordance with the invention it ispreferred here to apply the color layer to the substrate. Following fullcure through exposure to actinic radiation, the outer, carrier film canbe removed.

The bond to the substrate can be produced using adhesion promoters. Inaccordance with the invention it is preferred to use adhesives. In thiscontext it is preferred in turn to use UV-curing adhesives. UV radiationis used here preferably for adjusting the adhesive properties. Adhesivesof this kind are commercial products and are sold, for example, by BASFAktiengesellschaft under the brand name Acronal® 258 UV. In this casethe adhesive layer is preferably applied to a separate film and after UVcoating to the topcoat layer. This method is especially advantageous ifthe topcoat layer is a dual cure system.

Where transparent substrates are used for actinic radiation, fullcrosslinking of the adhesives by means of radiation is possible. Theadhesive properties are in this case adjustable preferably bypreliminary crosslinking by means of actinic radiation. Adhesivessuitable for this purpose are described, for example, in Römpp ChemieLexikon, 9th edition, volume 3, Georg Thieme Verlag, Stuttgart, 1990,“Adhesives”, pages 2252 to 2255. Of these adhesives, theradiation-curable adhesives based on (meth)acrylates or UP resins (cf.Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart,N.Y., 1998, “Unsaturated polyester resins”, pages 591 and 592, or D.Stoye and W. Freitag (Editors), Paint, Coatings and Solvents, Wiley-VCH,Weinheim, N.Y., 2nd, completely revised edition, 1998, “2.8. UnsaturatedPolyester Coatings, 2.8.1. Unsaturated Polyester Binders”, pages 57 to58) and styrene and/or (meth)acrylates are of advantage and aretherefore used with preference. It is also possible for theradiation-curable adhesives to include the radiation-curableconstituents described above.

UV systems require reinforcing sheets coated on both sides. Conventionalpressure-sensitive adhesives can be applied directly to the topcoatlayer.

The thickness of the adhesives is preferably between 4 μm and 20 μm.

The reinforcing sheet is preferably applied to the adhesive present onthe pigmented paint layer. Given appropriate reactivity of thereinforcing sheet, by adhesion promoters, for example, the adhesivelayer can be omitted. The outer face of the reinforcing sheet ispreferably provided in turn with an adhesive. Up until processing, thisadhesive can be lined with a removable release film.

With the existing adhesives, the removal of the paint films causesproblems. Depending on manufacturer, there is a requirement that thecoated films be removable again from the substrate without residue evenafter four years.

Complete reremovability can be achieved in accordance with theinvention, surprisingly, by virtue of the additional reinforcing sheet.In accordance with the invention this sheet has a thickness ofpreferably between 20 μm and 50 μm. From 20 μm to 30 μm are particularlypreferred. A preferred material is polypropylene.

An adhesive may be applied to the second paint layer. It can be pouredon, laminated or transferred. Atop it it is possible for there to beapplied a further film having a preferred thickness of ≦1000 μm,preferably ≦500 μm.

The paint film is cold-formable (deep-drawable) and can therefore bedrawn onto any structured area at room temperature or, whereappropriate, with slight heating in order to facilitate operation. Thefilms coated in accordance with the invention achieve thermoformabilityif a further film is laminated onto the adhesive layer present on thepigmented paint layer. Such further films are generally relatively thickfilms. The invention prefers films from 300 μm to 1 000 μm. From 400 μmto 700 μm are particularly preferred. Particularly suitable for thispurpose are ASA, ABS, and ASA-PC.

Stable 3D structures can be produced from the assembly by thermoforming.A prerequisite for this is effective drying of the laminate. The surfaceproperties of gloss, metallic, and flop effects are unaffected byforming.

The present invention also relates to a process for producing theabovementioned coated films. In this process the individual paint layerscan be applied either in succession or, preferably, by means ofapproximate simultaneous coating. In the latter process the layers areapplied directly wet on wet at short intervals of time. Thereafter thesystem is dried thermally in a drying tunnel. The purpose of drying is,in particular, to remove the solvent.

The coated films produced in accordance with the invention can beemployed wherever substrates require painting. Substrates of steel,aluminum, and plastic, in particular, can be coated. One preferredsphere of application is the motor vehicle industry. For rail vehiclesas well, however, i.e., locomotives and cars, the system of theinvention can be used to good effect. The scope of use embraces contraststripes through to full coating systems. A particular advantage here isthe possibility of removing the paint films again. Indeed, in that way,it is possible to produce new partial coatings of the vehicles withparticular ease. The removability is a further advantage in cases ofvandalism, e.g., as a result of daubing or spraying with paint(graffiti). Furthermore, the carrier film can ensure protection of thepaint surfaces until the end product has been produced. Thus, forexample, ready-made bodywork parts can first of all be injectionbackmolded or foam-backed, with the carrier film being removed onlyafter this operation is concluded.

In the text below the invention is described in more detail withreference to the figures.

FIG. 1 shows a layer construction made up of carrier film, clearcoatpaint, and color paint, and also an adhesive.

FIG. 2 shows a structure of an inventively coated film with reinforcingsheet.

FIG. 3 shows a structure of an inventively coated film havingparticularly good thermoforming properties.

FIG. 4 depicts an application method for producing the inventivelycoated films.

The coated film 1 depicted in FIG. 1 is composed of a polypropylenecarrier film 50 μm thick, a clearcoat 2 40 μm thick, and a color coat 330 μm thick, and also an adhesive 4 20 μm thick. Tests have indicatedthat the formability of these coated films is excellent. At the sametime the thermal stability is sufficient for production. With a driergradient of 30° C./60° C./105° C., the running and winding behavior inthe coating machine is good.

The structure reproduced in FIG. 2 shows a polypropylene carrier film 150 μm thick, and also a UV clearcoat layer 2 40 μm thick, a color coat 330 μm thick, and an adhesive 4 20 μm thick. Laminated to this adhesive 4is a reinforcing sheet 5 of from 25 μm to 50 μm. A further adhesive 6 20μm thick is then used to laminate a removable release film 7.

UV Acronal adhesive (Acronal 248 UV, BASF) was used as adhesive 4 and 6.Tests have shown that the coated films adhere effectively attemperatures between −30° C. and +90° C. to substrates such as steel,aluminum, plastic, and primed metal panels. The coated films wereremovable, without tears forming in the coating system on removal.Residues on the substrate were no longer present.

The structure depicted in FIG. 3 shows a polypropylene film 1 50 μmthick, a UV clearcoat 2 40 μm thick, a color layer 3 30 μm thick, anadhesive 4, and a film 8 500 μm thick. In accordance with the invention,Luran S was used for this.

This coated film was used to conduct thermoforming tests. After verygood drying of the assembly, the system was readily formable withretention of the surface quality. Gloss, metallic, and color flopeffects were unaffected by the forming. Formed parts can be injectionbackmolded or foam-backed, in accordance with the invention. In thiscase the protective film is preferably not removed until after formingand radiation crosslinking. The advantage of the present invention istherefore that the surface is protected from scratching during transportand processing by the protective film. The protective film has thefurther advantage that there is no oxygen inhibition on UV crosslinking.

FIG. 4 depicts by way of example the production of the inventivelycoated films. The carrier film 1, supplied on a roll, is guided beneatha predosed casting system 9. In the example according to FIG. 4 thissystem 9 includes the stations 11 and 12. By way of station 11 theclearcoat 2 is supplied via station 12 to the colorcoat 3. First of allthe clearcoat 2 goes onto the film 1 and by way of station 12 thecolorcoat 3 is applied simultaneously, so to speak, wet-on-wet. Film andpaint layers are then passed through a drier 13. The formation ofbubbles observed from a wet layer application of 30 μm up, as a resultof excessively rapid solvent release in the drier, was eliminated byadapting the temperature in the drying tunnel and by adding 10% of butylacetate (high boiler) to the acetone solution of clearcoat.

As an alternative the casting system may also be composed of two castingheads in series but spatially separate. The first caster applies theclearcoat layer to the film. Directly, in wet-on-wet process, thetopcoat layer is applied beneath the second casting head. The clearcoatlayer is applied using KRRC processes or, preferably, predosed castersor what are called blade coaters. The topcoat layer is applied usingpredosed casters or, preferably, extrusion casters, with a spreader lipto smooth the coating.

Irrespective of whether a casting system according to item 9 in FIG. 4or a system with separate casting units is used, it is necessary toensure that no mixing takes place between the boundary layers. To thisextent the two casting methods described guarantee, in the case ofwet-on-wet application, the absence of mixing of the clearcoat layer andof the topcoat layer.

After the drier, the coated film is supplied for further processing.

1. A film comprising a carrier film coated with at least two paintlayers, wherein the carrier film is coated with at least one first paintlayer, which is radiation-curable, and the first paint layer is coatedwith at least one second paint layer, which is curable at least partlywithout radiation, and wherein an adhesive layer has been cast,laminated or transferred onto the second paint layer.
 2. The film asclaimed in claim 1, wherein the second paint layer is curable thermallyand by radiation.
 3. The film as claimed in claim 1, wherein the firstlayer is an unpigmented clearcoat layer.
 4. The film as claimed in claim1, wherein the second paint layer is a pigmented topcoat layer.
 5. Thefilm as claimed in claim 1, wherein the first and the second paintlayers are curable by UV radiation.
 6. The film as claimed in claim 1,wherein the first paint layer has a thickness of 1 μm-400 μm and thesecond paint layer has a thickness of from 10 μm to 60 μm.
 7. The filmas claimed in claim 1, wherein the adhesive properties are adjustable bypreliminary crosslinking with actinic radiation.
 8. The film as claimedin claim 7, wherein the adhesive is curable by UV radiation.
 9. The filmas claimed in claim 6, wherein the thickness of the adhesive is 4 μm-20μm.
 10. The film as claimed in claim 1, wherein the carrier film isformable and thermally stable.
 11. The film as claimed in claim 10,wherein the carrier film comprises polypropylene.
 12. The film asclaimed in claim 10, wherein the carrier film has a thickness of from 40μm to 100 μm.
 13. The film as claimed in claim 10, wherein the carrierfilm has a thickness of from 50 μm to 70 μm.
 14. The film as claimed inclaim 1, wherein one or more further films have been applied to theadhesive layer.
 15. The film as claimed in claim 14, wherein one of thefurther films is a reinforcing sheet having a thickness of from 25 μm to50 μm.
 16. The film as claimed in claim 14, wherein to produce athermoformable assembly a further film with a thickness of ≦1000 μm isapplied to the adhesive layer.
 17. A process for producing the film asclaimed in claim 1, wherein the first and the second paint layers areapplied to the carrier film by approximate simultaneous coating in awet-on-wet application process and subsequently the solvent is removedfrom this system by thermal drying.
 18. The process as claimed in claim17, wherein an adhesive-coated release film is laminated or transferredonto the second paint layer.
 19. A substrate coated with the film asclaimed in claim 1, wherein the substrate is at least one of steel,aluminum or plastic.
 20. A process for coating a substrate comprising,coating a steel, aluminum or plastic substrate with the film as claimedin claim 1.